The emergence of the mystery former official whose late-night telephone call prompted broadcaster Allen Lee Peng-fei to quit his job has done little to clear up this baffling affair.

We now know that the man who made the call to Mr Lee is Cheng Shousan, former deputy director of the Foreign Ministry's Hong Kong and Macau Affairs Office. His account does not differ much from that of Mr Lee so far as the content of the call is concerned. But when it comes to the motives behind it - or how the conversation might be interpreted - they differ sharply.

According to Mr Cheng, the call was entirely innocent and not intended to apply pressure to the veteran politician and Teacup in a Storm host. It was simply an attempt to look up an old friend. The former official expressed amazement at the controversy his action caused.

Mr Lee, as revealed in his statement to lawmakers last week, views the call very differently. It is easy to understand why. The call was unexpected and made late in the evening. It came - as has now been confirmed - from a former official of some seniority. The caller made references to Mr Lee's 'virtuous wife' and 'beautiful daughter'. And, according to Mr Lee, he wanted to talk about the radio show.

The timing of the call is crucial. It followed a number of attempts by mainland figures to put pressure on Mr Lee to tone down the forthright views he expressed on the talk show.

Two other, even more outspoken, broadcasters with similar opinions had already stepped down in an apparent response to pressure.

We will never know precisely where the truth lies. Mr Lee may have been feeling so much stress that he misinterpreted the motives behind the call. He may have mistaken an innocent inquiry from a long-forgotten acquaintance for a sinister attempt to suppress his freedom of expression. It would be surprising if a politician of Mr Lee's experience made such a mistake but it is possible.

However, even if we accept Mr Cheng's version of events, the incident serves to underline the need to rigorously protect freedom of expression in our city. If a political heavyweight such as Mr Lee feels intimidated by what the former official maintains was a well-intentioned call to his home, it says much about the unhealthy climate existing in Hong Kong.

The decision by Mr Lee to go public with the circumstances that led him to resign has had at least one positive result. It led Chief Executive Tung Chee-hwa to break his silence and speak out in defence of the freedom of expression.

It is important that the government continues to provide strong, public support for our values and our rights. Hong Kong people, too, have a central role to play. They should not be paranoid, but need to remain vigilant. And they should keep on speaking their mind. This is the best way to defend our freedoms.